富水软弱围岩偏压隧道超前支护施工技术研究

Research of Advance Support Construction Technology for Water-rich Weak Surrounding Rock Bias Tunnel

研究了富水软弱围岩偏压隧道超前支护及施工技术.依托国家一带一路重点项目云南临沧临翔至清水河高速公路马家寨隧道工程,通过有限元软件MIDAS GTS NX建立有无超前支护的隧道出口端有限元模型,分析无超前支护和长管棚超前支护工况下隧道围岩稳定性、初期支护应力及围岩塑性区的变化规律.结果表明:随着隧道开挖,拱顶沉降越来越大,无超前支护工况下隧道开挖完成后最大拱顶沉降为9.56 mm,长管棚超前支护工况下拱顶沉降降低了44.9%.针对围岩变形而言,在长管棚超前支护条件下围岩最大竖向变形降低了48.0%,最大Y方向变形降低了50.4%.在无超前支护工况下,初期支护最大压应力超过规范允许值13.5 MPa,长管棚超前支护工况下最大初期支护压应力为11.47 MPa.长管棚超前支护能够有效控制富水软弱围岩隧道偏压段的围岩变形,改善结构受力状态,确保隧道进洞施工安全.

Advance support construction technology for water-rich weak surrounding rock bias tunnel is studied.Taking the national One Belt and One Road key project,Majiazhai Tunnel on the Linxiang-Qingshuihe Expressway in Lincang of Yunnan province as the engineering background,a finite element model of tunnel excavation was established with or without advance support by finite element software MIDAS GTS NX.In addition,the variation of surrounding rock stability,primary support stress and plastic zone of surrounding rock under the condition of advanced support without long-term support and long pipe shed were analyzed.The results show that,with the excavation of tunnel,the settlement of vault becomes larger and larger.The maximum arch settlement after the completion of tunnel excavation without pre-supporting conditions is 9.56 mm.The arch settlement of the long pipe shed was reduced by 44.9%under the condition of advanced support.For the deformation of surrounding rock,the maximum vertical deformation of surrounding rock decreased by 48.0%under the condition of advanced support of long pipe shed,the maximum Y direction deformation is reduced by 50.4%.In the absence of advanced support conditions,the maximum compressive stress of the primary support exceeds the allowable value of 13.5 MPa.The maximum primary support compressive stress of the long pipe shed under the advanced support condition is 11.47 MPa.Long tube shed advanced support can effectively control the surrounding rock deformation of the biased section of the water-rich weak surrounding rock tunnel,improve structural stress state,and ensure the safty of tunnel construction.